Characterization of crude oil and its fractions by fluorescence spectroscopy analysis

ABSTRACT

A system and a method are provided for calculating the cetane number, pour point, cloud point, aniline point, aromaticity, and/or octane number of a crude oil and its fractions from the density and fluorescence spectroscopy of a sample of the crude oil.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Patent Application No. 62/099,703 filed Jan. 5, 2015, the disclosure of which is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

This invention relates to a method and process for the evaluation of samples of crude oil and its fractions by fluorescence spectroscopy analysis.

BACKGROUND OF THE INVENTION

Crude oil originates from the decomposition and transformation of aquatic, mainly marine, living organisms and/or land plants that became buried under successive layers of mud and silt some 15-500 million years ago. They are essentially very complex mixtures of many thousands of different hydrocarbons. Depending on the source, the oil predominantly contains various proportions of straight and branched-chain paraffins, cycloparaffins, and naphthenic, aromatic, and polynuclear aromatic hydrocarbons. These hydrocarbons can be gaseous, liquid, or solid under normal conditions of temperature and pressure, depending on the number and arrangement of carbon atoms in the molecules.

Crude oils vary widely in their physical and chemical properties from one geographical region to another and from field to field. Crude oils are usually classified into three groups according to the nature of the hydrocarbons they contain: paraffinic, naphthenic, asphaltic, and their mixtures. The differences are due to the different proportions of the various molecular types and sizes. One crude oil can contain mostly paraffins, another mostly naphthenes. Whether paraffinic or naphthenic, one can contain a large quantity of lighter hydrocarbons and be mobile or contain dissolved gases; another can consist mainly of heavier hydrocarbons and be highly viscous, with little or no dissolved gas. Crude oils can also include heteroatoms containing sulfur, nitrogen, nickel, vanadium and other elements in quantities that impact the refinery processing of the crude oil fractions. Light crude oils or condensates can contain sulfur in concentrations as low as 0.01 W %; in contrast, heavy crude oils can contain as much as 5-6 W %. Similarly, the nitrogen content of crude oils can range from 0.001-1.0 W %. The nature of the crude oil governs, to a certain extent, the nature of the products that can be manufactured from it and their suitability for special applications. A naphthenic crude oil will be more suitable for the production of asphaltic bitumen, a paraffinic crude oil for wax. A naphthenic crude oil, and even more so an aromatic one, will yield lubricating oils with viscosities that are sensitive to temperature. However, with modern refining methods there is greater flexibility in the use of various crude oils to produce many desired type of products.

A crude oil assay is a traditional method of determining the nature of crude oils for benchmarking purposes. Crude oils are subjected to true boiling point (TBP) distillations and fractionations to provide different boiling point fractions. The crude oil distillations are carried out using the American Standard Testing Association (ASTM) Method D 2892. The common fractions and their nominal boiling points are given in Table 1.

TABLE 1 Fraction Boiling Point, ° C. Methane −161.5  Ethane −88.6 Propane −42.1 Butanes  −6.0 Light Naphtha 36-90 Mid Naphtha  90-160 Heavy Naphtha 160-205 Light gas Oil 205-260 Mid Gas Oil 260-315 Heavy gas Oil 315-370 Light Vacuum Gas Oil 370-430 Mid Vacuum Gas Oil 430-480 Heavy vacuum gas oil 480-565 Vacuum Residue 565+ 

The yields, composition, physical and indicative properties of these crude oil fractions, where applicable, are then determined during the crude assay work-up calculations. Typical compositional and property information obtained from a crude oil assay is given in Table 2.

TABLE 2 Property Unit Property Type Fraction Yield Weight and Volume % W % Yield All API Gravity ° Physical All Viscosity Kinematic @ 38° C. ° Physical Fraction boiling >250° C. Refractive Index @ 20° C. Unitless Physical Fraction boiling <400° C. Sulfur W % Composition All Mercaptan Sulfur, W % W % Composition Fraction boiling <250° C. Nickel ppmw Composition Fraction boiling >400° C. Nitrogen ppmw Composition All Flash Point, COC ° C. Indicative All Cloud Point ° C. Indicative Fraction boiling >250° C. Pour Point, (Upper) ° C. Indicative Fraction boiling >250° C. Freezing Point ° C. Indicative Fraction boiling >250° C. Micro Carbon Residue W % Indicative Fraction boiling >300° C. Smoke Point, mm mm Indicative Fraction boiling between 150-250° C. Octane Number Unitless Indicative Fraction boiling <250° C. Cetane Index Unitless Indicative Fraction boiling between 150-400° C. Aniline Point ° C. Indicative Fraction boiling <520° C.

Due to the number of distillation cuts and the number of analyses involved, the crude oil assay work-up is both costly and time consuming.

In a typical refinery, crude oil is first fractionated in the atmospheric distillation column to separate sour gas and light hydrocarbons, including methane, ethane, propane, butanes and hydrogen sulfide, naphtha (36-180° C.), kerosene (180-240° C.), gas oil (240-370° C.) and atmospheric residue (>370° C.). The atmospheric residue from the atmospheric distillation column is either used as fuel oil or sent to a vacuum distillation unit, depending on the configuration of the refinery. The principal products obtained from vacuum distillation are vacuum gas oil, comprising hydrocarbons boiling in the range 370-520° C., and vacuum residue, comprising hydrocarbons boiling above 520° C. Crude assay data is conventionally obtained from individual analysis of these cuts to help refiners to understand the general composition of the crude oil fractions and properties so that the fractions can be processed most efficiently and effectively in an appropriate refining unit. Indicative properties are used to determine the engine/fuel performance or usability or flow characteristic or composition. A summary of the indicative properties and their determination methods with description is given below.

The cetane number of diesel fuel oil, determined by the ASTM D613 method, provides a measure of the ignition quality of diesel fuel; as determined in a standard single cylinder test engine; which measures ignition delay compared to primary reference fuels. The higher the cetane number; the easier the high-speed; direct-injection engine will start; and the less white smoking and diesel knock after start-up are. The cetane number of a diesel fuel oil is determined by comparing its combustion characteristics in a test engine with those for blends of reference fuels of known cetane number under standard operating conditions. This is accomplished using the bracketing hand wheel procedure which varies the compression ratio (hand wheel reading) for the sample and each of the two bracketing reference fuels to obtain a specific ignition delay, thus permitting interpolation of cetane number in terms of hand wheel reading.

The cloud point, determined by the ASTM D2500 method, is the temperature at which a cloud of wax crystals appears when a lubricant or distillate fuel is cooled under standard conditions. Cloud point indicates the tendency of the material to plug filters or small orifices under cold weather conditions. The specimen is cooled at a specified rate and examined periodically. The temperature at which cloud is first observed at the bottom of the test jar is recorded as the cloud point. This test method covers only petroleum products and biodiesel fuels that are transparent in 40 mm thick layers, and with a cloud point below 49° C.

The pour point of petroleum products, determined by the ASTM D97 method, is an indicator of the ability of oil or distillate fuel to flow at cold operating temperatures. It is the lowest temperature at which the fluid will flow when cooled under prescribed conditions. After preliminary heating, the sample is cooled at a specified rate and examined at intervals of 3° C. for flow characteristics. The lowest temperature at which movement of the specimen is observed is recorded as the pour point.

The aniline point, determined by the ASTM D611 method, is the lowest temperature at which equal volumes of aniline and hydrocarbon fuel or lubricant base stock are completely miscible. A measure of the aromatic content of a hydrocarbon blend is used to predict the solvency of a base stock or the cetane number of a distillate fuel. Specified volumes of aniline and sample, or aniline and sample plus n-heptane, are placed in a tube and mixed mechanically. The mixture is heated at a controlled rate until the two phases become miscible. The mixture is then cooled at a controlled rate and the temperature at which two separate phases are again formed is recorded as the aniline point or mixed aniline point.

The octane number, determined by the ASTM D2699 or D2700 methods, is a measure of a fuel's ability to prevent detonation in a spark ignition engine. Measured in a standard single-cylinder; variable-compression-ratio engine by comparison with primary reference fuels. Under mild conditions, the engine measures research octane number (RON), while under severe conditions, the engine measures motor octane number (MON). Where the law requires posting of octane numbers on dispensing pumps, the antiknock index (AKI) is used. This is the arithmetic average of RON and MON, (R+M)/2. It approximates the road octane number, which is a measure of how an average car responds to the fuel.

To determine these properties of gas oil or naphtha fractions conventionally, these fractions have to be distilled from the crude oil and then measured/identified using various analytical methods that are laborious, costly and time-consuming.

Fluorescence spectrometry is a sensitive and selective analytical method for aromatic-containing samples like crude oil. Therefore, it is particularly useful for the determination of condensed aromatic or heteroaromatic ring compounds in crude oil. Fluorescence occurs when a fluorescent material is excited by absorbing an incident light (photon) into a higher electronic state which will return to the ground state after emitting light (a photon) from the ground vibrational level of the excited electronic state. The emitted photon goes to an excited vibrational state of the ground electronic state. The structure and environments of the fluorescent material can be deduced from the energies and relative intensities of the fluorescence signals.

A fluorescence emission spectrum is recorded when the excitation wavelength of light is held constant and the emission beam is scanned as a function of wavelength. An excitation spectrum is the opposite, whereby the emission light is held at a constant wavelength, and the excitation light is scanned as a function of wavelength. The excitation spectrum usually resembles the absorbance spectrum in shape.

Synchronous fluorescence spectrometry is the method of choice to improve the selectivity of the measurement by taking full advantage of the ability to vary both the excitation and the emission wavelength during analysis. Excitation and emission wavelengths are scanned simultaneously while maintaining a constant wavelength difference between the two modes. This method has been proved successful for materials like polycyclic aromatic hydrocarbons.

This invention discloses a system and method in which fluorescence spectroscopy analysis is employed to disclose physical and indicative properties (i.e., cetane number, pour point, cloud point, and aniline point) of gas oil fraction of crude oils, as well as the octane number of the naphtha fraction and the aromaticity of whole crude oils. The invention provides insight into the gas oil properties without fractionation/distillation (crude oil assays) and will help producers, refiners, and marketers to benchmark the oil quality and, as a result, valuate the oils without going thru costly and time consuming crude oil assays. Whereas a conventional crude oil assay method could take up to two months, this invention provides results within one hour.

New rapid, and direct methods to help better understand crude oil compositions and properties from analysis of whole crude oil will save producers, marketers, refiners and/or other crude oil users substantial expense, effort and time. Therefore, a need exists for an improved system and method for determining indicative properties of crude oil fractions from different sources.

SUMMARY OF THE INVENTION

Systems and methods for determining one or more indicative properties of a hydrocarbon sample are presented. Indicative properties in a crude oil sample (e.g., cetane number, pour point, cloud point and aniline point) of a gas oil fraction, octane number of a naphtha fraction, and the aromaticity for the whole crude oil (WCO), are assigned as a function of density and fluorescence spectroscopy measurement of a crude oil sample. The indicative properties provide information about the gas oil and naphtha properties without fractionation/distillation (crude oil assays) and help producers, refiners, and marketers to benchmark the oil quality and, as a result, valuate the oils without performing the customary extensive and time-consuming crude oil assays.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages and features of the present invention will become apparent from the following detailed description of the invention when considered with reference to the accompanying drawings in which:

FIG. 1 is a graphic plot of typical fluorescence spectroscopy data for typical crude oil samples with different API gravities;

FIG. 2 is a block diagram of a method in which an embodiment of the invention is implemented;

FIG. 3 is a schematic block diagram of modules of an embodiment of the invention; and

FIG. 4 is a block diagram of a computer system in which an embodiment of the invention is implemented.

DETAILED DESCRIPTION OF INVENTION

A system and a method are provided for determining one or more indicative properties of a hydrocarbon sample. Indicative properties (e.g., cetane number, pour point, cloud point, and aniline point) of a gas oil fraction and ozone number of a naphtha fraction in a crude oil sample are assigned as a function of the density and fluorescence spectroscopy measurement of the crude oil sample. The indicative properties provide information about the gas oil and naphtha properties without fractionation/distillation (crude oil assays) and help producers, refiners, and marketers to benchmark the oil quality and, as a result, valuate the oils without performing the customary extensive and time-consuming crude oil assays.

The systems and methods are applicable for naturally occurring hydrocarbons derived from crude oils, bitumens, heavy oils, shale oils and from refinery process units including hydrotreating, hydroprocessing, fluid catalytic cracking, coking, and visbreaking or coal liquefaction.

In the system and method herein, fluorescence spectroscopy analysis is obtained by a suitable known or to-be-developed process. Fluorescence spectroscopy uses a fluorometer to collect spectral data of a solid, liquid, or gas.

In one embodiment, a Varian Cary Eclipse fluorescence spectrophotometer (i.e., fluorometer) was used for the analysis of the crude oil. The synchronization scanning mode was utilized, with a delta of 15 nm, and a scan range from 250-800 nm.

Typical fluorescence spectroscopy data for crude oils with different API gravities is shown in FIG. 1.

In one embodiment, the fluorescence spectroscopy index is calculated as follows. The absorbance unit at each wavelength (integer) of the scan range is summed, and then the total is divided by 1000.

$\begin{matrix} {{FSMI}_{crude\_ oil} = {\sum\limits_{f = 250}^{800}\; {\left( {{Absorbance}\mspace{14mu} {Unit}} \right)/(1000)}}} & (1) \end{matrix}$

FIG. 2 shows a process flowchart of steps in a method according to one embodiment herein, in which crude oil samples are prepared and analyzed by fluorescence spectroscopy according to the method 200 described below.

In step 210 a sample of crude oil is dissolved in hexane and then scanned by the fluorometer over the wavelength range from 250-800 nm.

In step 215, the fluorescence spectroscopy data is arranged by wavelength and absorbance unit.

In step 220, a fluorescence spectroscopy index is calculated according to equation (1).

The indicative properties (e.g., the cetane number, pour point, cloud point and aniline point) of the gas oil fraction, e.g. boiling in the range of 150-400° C. and in certain embodiments in the range of 180-370° C., the octane number of the naphtha fraction, and the aromaticity for the whole crude oil (WCO), can be assigned as a function of the density and the fluorescence spectroscopy index of crude oil. That is,

Indicative Property=f(density_(crude oil) ,FSMI _(crudeoil))  (2);

Equation (3) is a detailed example of this relationship, showing the cetane number, pour point, cloud point and aniline point that can be predicted for the gas oil (GO) fraction of the crude oil, as well as the aromaticity that can be predicted for the whole crude oil (WCO), as well as the octane number that can be predicted for the naphtha fraction.

In steps 235, 240, 245, and 250, respectively, the properties of a cetane number, pour point, cloud point and aniline point for the gas oil (GO) fraction of the crude oil are calculated, in step 253 the aromaticity for the whole crude oil (WCO) is calculated, and in step 255 the property of an octane number for the naphtha fraction of the crude oil is calculated. While FIG. 2 shows the steps performed sequentially, they can be performed in parallel or in any order. In certain embodiments, only one or more steps 235, 240, 245, 250, 253, 255 are carried out. In these steps, the one or more indicative properties are determined as follows:

Indicative property=K+X1*DEN+X2*DEN² +X3*DEN³ +X4*FSMI+X5*FSMI ² +X6*FSMI ³ +X7*DEN*FSMI  (3);

where:

DEN=density of the crude oil sample; and

K, X1-X7, are constants for the properties to be predicted that are developed using linear regression analysis of hydrocarbon data from fluorescence spectrometry data.

FIG. 3 illustrates a schematic block diagram of modules in accordance with an embodiment of the present invention, system 300. Density and raw data receiving module 310 receives the density of a sample of crude oil and fluorescence spectroscopy data derived from the crude oil.

Fluorescence spectroscopy index calculation module 315 calculates the fluorescence spectroscopy index from the spectral data.

Cetane number calculation module 335 derives the cetane number for the gas oil fraction of the crude oil as a function of the fluorescence spectroscopy index and density of the sample.

Pour point calculation module 340 derives the pour point for the gas oil fraction of the crude oil as a function of the fluorescence spectroscopy index and density of the sample.

Cloud point calculation module 345 derives the cloud point for the gas oil fraction of the crude oil as a function of the fluorescence spectroscopy index and density of the sample.

Aniline point calculation module 350 derives the aniline point for the gas oil fraction of the crude oil as a function of the fluorescence spectroscopy index and density of the sample.

Aromaticity calculation module 352 derives the aromaticity for the whole crude oil as a function of the fluorescence spectroscopy index and density of the sample.

Octane number calculation module 355 derives the octane number for the naphtha fraction of the crude oil as a function of the fluorescence spectroscopy index and density of the sample.

FIG. 4 shows an exemplary block diagram of a computer system 400 in which one embodiment of the present invention can be implemented. Computer system 400 includes a processor 420, such as a central processing unit, an input/output interface 430 and support circuitry 440. In certain embodiments, where the computer system 400 requires a direct human interface, a display 410 and an input device 450 such as a keyboard, mouse or pointer are also provided. The display 410, input device 450, processor 420, and support circuitry 440 are shown connected to a bus 490 which also connects to a memory 460. Memory 460 includes program storage memory 470 and data storage memory 480. Note that while computer system 400 is depicted with direct human interface components display 410 and input device 450, programming of modules and exportation of data can alternatively be accomplished over the input/output interface 430, for instance, where the computer system 400 is connected to a network and the programming and display operations occur on another associated computer, or via a detachable input device as is known with respect to interfacing programmable logic controllers.

Program storage memory 470 and data storage memory 480 can each comprise volatile (RAM) and non-volatile (ROM) memory units and can also comprise hard disk and backup storage capacity, and both program storage memory 470 and data storage memory 480 can be embodied in a single memory device or separated in plural memory devices. Program storage memory 470 stores software program modules and associated data, and in particular stores a density and raw data receiving module 310, fluorescence spectroscopy index calculation module 315, cetane number calculation module 335, pour point calculation module 340, cloud point calculation module 345, aniline point calculation module 350, aromaticity calculation module 352, and octane number calculation module 355. Data storage memory 480 stores results and other data generated by the one or more modules of the present invention.

It is to be appreciated that the computer system 400 can be any computer such as a personal computer, minicomputer, workstation, mainframe, a dedicated controller such as a programmable logic controller, or a combination thereof. While the computer system 400 is shown, for illustration purposes, as a single computer unit, the system can comprise a group of computers which can be scaled depending on the processing load and database size.

Computer system 400 preferably supports an operating system, for example stored in program storage memory 470 and executed by the processor 420 from volatile memory. According to an embodiment of the invention, the operating system contains instructions for interfacing computer system 400 to the Internet and/or to private networks.

Example 1

A set of constants K and X1-X7 was determined using linear regression for the indicative properties cetane number, pour point, cloud point, aniline point, octane number, and aromaticity. These constants were determined based on known actual distillation data for plural crude oil samples and their corresponding indicative properties. These constants are given in Table 3.

TABLE 3 Constants Cetane Number Pour Point Cloud Point K −2.920657E+04 −2.283807E+04 8.016178E+04 X1 8.247657E+04 6.995129E+04 −2.781445E+05 X2 −8.008823E+04 −7.232753E+04 3.199487E+05 X3 2.758504E+04 2.532512E+04 −1.219746E+05 X4 1.273387E+02 4.791017E+01 3.108188E+01 X5 4.207752E−01 −8.303909E−02 1.963374E−01 X6 −4.676128E−03 7.142002E−04 −1.983566E−03 X7 −1.581570E+02 −5.156225E+01 −4.212763E+01 Constants Aniline Point Octane Number WCO-AROM K −4.370054E+04 1.017323E+05 1.047903E+04 X1 1.449824E+05 −3.438191E+05 −4.741776E+04 X2 −1.608909E+05 3.877252E+05 6.274074E+04 X3 5.979962E+04 −1.457003E+05 −2.516125E+04 X4 2.649713E+01 −9.217455E+00 8.586987E+01 X5 −5.686953E−02 2.914821E−01 6.843602E−01 X6 3.346494E−04 −2.737219E−03 −7.078907E−03 X7 −2.749938E+01 0.000000E+00 −1.207479E+02

The following example is provided to demonstrate an application of equations (3). A sample of Arabian medium crude with a 15° C./4° C. density of 0.8828 Kg/1 was analyzed by fluorescence spectroscopy, using the described method. The tabulated results follow in Table 4:

TABLE 4 API Gravity, ° Wavelength (nm) 28.8 19.6 250 1.27 1.05 251 1.21 0.91 252 1.14 0.85 253 0.95 1.02 254 0.97 0.92 255 1.15 0.94 256 1.28 1.09 257 1.33 1.44 258 1.57 1.44 259 1.83 1.63 260 2.05 1.96 261 2.63 2.21 262 3.16 2.73 263 3.74 3.25 264 4.28 3.88 265 5.00 5.07 266 5.67 5.59 267 6.48 6.78 268 6.65 7.27 269 7.56 8.55 270 7.85 9.29 271 8.36 9.87 272 8.71 10.68 273 8.93 11.21 274 9.24 11.49 275 8.79 12.13 276 8.60 12.45 277 8.79 12.68 278 8.35 12.72 279 7.74 12.31 280 7.50 12.34 281 7.35 12.60 282 7.42 12.55 283 7.79 13.13 284 9.11 14.59 285 10.15 16.48 286 12.32 19.70 287 14.84 23.30 288 17.17 27.11 289 20.36 31.74 290 22.93 36.59 291 24.17 40.13 292 26.52 44.18 293 28.00 46.89 294 27.89 49.52 295 28.54 51.24 296 29.29 54.14 297 30.29 56.46 298 30.41 58.06 299 31.50 60.48 300 31.99 62.98 301 32.14 63.77 302 32.38 66.72 303 31.66 66.79 304 31.23 67.48 305 29.79 66.10 306 28.95 65.39 307 27.11 64.41 308 26.08 63.97 309 25.76 62.65 310 25.31 62.52 311 24.73 62.68 312 25.28 64.40 313 26.44 67.67 314 27.19 69.71 315 27.25 68.99 316 28.15 70.95 317 29.82 73.39 318 31.36 78.28 319 32.10 81.73 320 34.13 85.19 321 34.44 87.23 322 37.79 94.02 323 40.61 101.62 324 43.34 109.60 325 46.36 117.56 326 47.79 124.76 327 51.11 134.00 328 54.09 143.32 329 56.67 152.26 330 58.77 159.16 331 58.02 159.37 332 60.10 165.95 333 61.49 168.93 334 63.50 176.30 335 63.66 172.61 336 63.59 173.20 337 62.73 175.41 338 65.47 181.41 339 68.17 184.71 340 69.14 188.76 341 68.81 184.04 342 70.78 187.74 343 71.17 186.11 344 74.48 194.29 345 74.95 192.86 346 75.31 196.13 347 76.25 191.86 348 76.99 192.92 349 77.96 192.59 350 80.27 194.30 351 78.27 190.40 352 77.50 188.90 353 77.98 184.87 354 78.21 187.44 355 78.16 185.91 356 78.36 184.15 357 76.17 178.69 358 76.24 175.44 359 75.49 174.06 360 76.48 175.46 361 75.71 173.24 362 77.62 172.86 363 77.05 169.22 364 78.20 171.83 365 77.52 167.50 366 79.23 167.43 367 77.33 161.66 368 78.10 161.76 369 76.25 156.31 370 77.04 153.14 371 75.00 151.36 372 76.69 151.51 373 76.13 148.03 374 75.95 147.92 375 74.56 146.40 376 77.28 153.98 377 78.71 157.11 378 80.95 165.33 379 81.67 167.60 380 83.41 174.64 381 86.26 181.18 382 87.37 189.91 383 88.30 194.12 384 90.10 196.70 385 89.27 199.14 386 91.91 204.95 387 92.77 210.50 388 91.22 210.57 389 91.49 210.34 390 90.72 211.38 391 90.54 209.72 392 91.19 213.29 393 92.41 216.90 394 92.39 218.13 395 93.00 220.83 396 93.93 220.46 397 94.01 222.20 398 93.90 222.32 399 93.41 223.02 400 92.18 221.82 401 91.00 220.53 402 91.43 219.05 403 91.29 218.84 404 92.06 218.51 405 91.49 219.09 406 92.58 218.48 407 91.94 216.00 408 91.44 216.14 409 92.37 215.76 410 91.80 212.67 411 90.76 210.61 412 89.27 209.16 413 89.74 205.68 414 89.07 203.71 415 88.22 200.33 416 87.09 198.86 417 87.18 197.27 418 86.86 195.36 419 86.88 195.24 420 87.05 195.64 421 87.44 195.13 422 87.04 194.82 423 87.33 192.77 424 87.21 192.40 425 87.65 191.73 426 87.08 191.12 427 87.11 189.04 428 85.32 187.05 429 85.49 184.34 430 83.64 180.80 431 83.72 177.67 432 83.13 178.84 433 83.41 177.03 434 83.70 175.80 435 82.78 175.25 436 81.67 173.03 437 81.69 172.99 438 81.69 170.94 439 81.37 170.17 440 81.09 169.31 441 80.69 169.08 442 79.95 167.44 443 79.43 165.50 444 78.64 163.07 445 78.29 161.13 446 78.06 160.86 447 77.39 159.34 448 76.72 158.48 449 76.97 157.38 450 76.05 154.39 451 74.74 153.40 452 74.13 151.33 453 73.35 148.34 454 72.50 146.80 455 71.39 144.42 456 70.29 140.20 457 69.49 139.33 458 67.91 136.19 459 67.47 136.30 460 66.83 134.80 461 66.13 133.01 462 65.91 132.51 463 64.99 129.55 464 64.42 127.25 465 62.81 125.11 466 61.35 121.38 467 60.41 119.99 468 59.29 118.29 469 59.48 116.76 470 57.97 114.85 471 57.34 113.47 472 56.76 112.23 473 54.83 109.40 474 54.62 107.56 475 53.24 105.06 476 52.40 103.80 477 51.24 102.89 478 50.54 100.46 479 49.71 98.76 480 48.71 95.76 481 46.65 91.87 482 46.75 92.08 483 45.58 91.72 484 45.47 90.16 485 44.77 90.37 486 44.22 89.52 487 44.13 88.40 488 42.93 87.33 489 41.99 85.13 490 41.09 83.09 491 40.30 81.43 492 39.87 81.19 493 39.07 79.56 494 38.61 78.01 495 37.54 76.65 496 36.22 75.01 497 35.59 73.99 498 35.13 71.41 499 34.20 71.86 500 34.18 70.05 501 32.85 69.17 502 31.72 67.31 503 31.47 66.49 504 30.76 64.14 505 30.20 63.20 506 29.32 62.69 507 29.02 61.29 508 27.78 59.76 509 27.66 58.69 510 27.14 58.04 511 27.02 56.90 512 26.38 56.02 513 25.72 55.28 514 25.03 53.66 515 24.12 52.39 516 24.26 51.68 517 23.67 50.34 518 22.48 49.83 519 22.56 48.20 520 22.12 48.16 521 21.43 46.61 522 20.92 45.44 523 20.12 44.67 524 19.80 43.49 525 19.30 41.61 526 18.87 41.21 527 18.46 40.69 528 18.36 40.39 529 18.06 39.71 530 17.67 39.44 531 17.75 38.55 532 16.95 37.58 533 16.58 36.48 534 16.11 35.58 535 15.88 35.02 536 15.72 34.58 537 15.33 33.95 538 14.77 32.36 539 14.15 31.44 540 13.74 31.22 541 13.51 30.52 542 13.34 30.13 543 13.22 29.26 544 13.03 29.66 545 12.49 28.66 546 12.34 28.03 547 11.71 27.70 548 11.95 27.46 549 11.78 27.10 550 11.40 26.31 551 11.10 25.65 552 10.85 25.14 553 10.40 24.94 554 10.11 24.16 555 10.30 23.22 556 10.01 23.19 557 9.85 22.60 558 8.94 22.71 559 9.08 22.36 560 9.14 21.25 561 8.91 20.57 562 8.48 20.23 563 8.41 19.76 564 8.33 18.95 565 8.13 19.24 566 7.50 18.61 567 7.78 17.66 568 7.69 17.33 569 7.45 17.61 570 7.12 17.31 571 6.95 17.03 572 6.82 16.17 573 6.63 16.20 574 6.43 15.86 575 6.71 15.62 576 6.40 15.06 577 6.37 14.35 578 6.13 14.40 579 6.28 14.51 580 6.08 13.72 581 5.51 13.78 582 5.54 13.23 583 5.53 13.24 584 5.29 13.22 585 5.72 12.35 586 5.00 12.14 587 4.98 12.07 588 4.82 11.48 589 4.81 12.04 590 4.79 11.35 591 4.52 11.28 592 4.46 10.10 593 4.32 10.52 594 4.28 10.09 595 3.88 9.88 596 4.10 9.57 597 4.18 9.47 598 3.96 9.79 599 3.80 9.14 600 3.78 8.88 601 3.67 8.30 602 3.43 8.49 603 3.49 7.82 604 3.28 7.81 605 3.13 7.45 606 3.02 7.76 607 3.29 7.62 608 3.43 7.53 609 2.84 7.36 610 2.95 7.37 611 2.87 6.67 612 2.72 6.99 613 2.64 6.74 614 2.52 6.59 615 2.52 6.29 616 2.60 6.30 617 2.56 6.07 618 2.24 5.60 619 2.74 5.61 620 2.47 5.92 621 2.19 5.51 622 2.03 5.41 623 2.37 5.22 624 2.09 5.13 625 1.75 5.14 626 1.71 4.92 627 2.15 5.04 628 1.93 5.05 629 1.72 4.74 630 2.01 4.89 631 1.66 4.58 632 1.95 4.53 633 1.55 4.44 634 2.03 4.36 635 1.58 4.14 636 2.00 3.74 637 1.52 3.30 638 1.32 3.85 639 1.23 3.82 640 1.77 4.04 641 1.55 3.56 642 1.67 3.38 643 1.22 4.22 644 0.91 3.78 645 1.64 3.38 646 1.23 3.97 647 1.51 3.16 648 1.53 3.30 649 1.41 3.55 650 1.29 2.64 651 1.47 3.08 652 1.35 2.82 653 1.22 2.66 654 1.13 3.13 655 1.33 2.87 656 1.26 3.11 657 1.08 2.09 658 1.33 2.52 659 0.98 2.46 660 1.11 2.75 661 1.19 2.34 662 1.06 2.20 663 1.07 2.86 664 1.08 2.43 665 1.10 2.58 666 1.22 2.34 667 0.94 2.20 668 1.20 2.27 669 0.71 2.07 670 1.31 1.99 671 0.43 2.20 672 0.81 1.48 673 0.84 1.90 674 0.91 2.07 675 0.39 1.79 676 0.82 2.07 677 1.05 1.47 678 1.13 2.14 679 1.20 1.85 680 0.68 1.99 681 0.81 1.50 682 0.30 1.87 683 1.03 1.52 684 1.03 2.16 685 0.50 1.90 686 1.02 1.91 687 0.67 1.58 688 0.65 1.51 689 0.51 1.43 690 0.44 0.97 691 0.79 1.73 692 0.93 1.19 693 0.94 1.40 694 0.84 1.35 695 0.66 1.36 696 0.99 1.20 697 0.73 0.89 698 0.48 1.71 699 0.68 1.29 700 0.43 1.74 701 0.58 1.96 702 0.70 1.07 703 0.78 1.19 704 0.69 1.35 705 0.95 1.17 706 −0.49 1.69 707 1.10 1.38 708 0.68 1.76 709 0.61 1.09 710 0.71 0.90 711 0.54 1.03 712 0.09 1.59 713 0.18 1.59 714 1.18 0.75 715 0.83 0.84 716 0.28 1.45 717 0.39 1.22 718 0.51 0.53 719 −0.22 1.01 720 0.36 1.35 721 0.37 0.90 722 0.00 0.13 723 0.65 1.08 724 0.93 1.09 725 1.22 0.70 726 1.08 0.28 727 −0.67 0.84 728 0.40 0.56 729 0.40 1.81 730 1.33 0.14 731 −0.13 1.12 732 0.81 0.84 733 −0.83 1.29 734 −0.28 1.63 735 0.60 0.47 736 −0.63 0.81 737 0.16 0.34 738 0.68 1.58 739 0.35 2.00 740 −0.90 1.68 741 0.37 1.34 742 0.00 −0.99 743 −0.59 0.40 744 0.20 1.04 745 0.60 2.53 746 −1.04 1.07 747 −0.62 1.32 748 −0.42 1.54 749 −0.21 0.00 750 −0.42 0.66 751 1.30 0.46 752 0.87 −0.23 753 0.00 0.46 754 0.22 0.70 755 −0.46 0.48 756 1.63 1.23 757 0.00 2.24 758 0.24 −0.25 759 0.00 0.75 760 1.92 −1.02 761 −0.24 2.00 762 −0.47 2.65 763 2.18 1.61 764 0.43 0.67 765 0.87 −0.45 766 0.45 0.95 767 −0.24 1.52 768 0.00 1.90 769 0.55 −0.28 770 −0.58 0.30 771 −0.90 0.62 772 0.31 1.27 773 1.57 0.97 774 0.96 0.34 775 −0.64 0.34 776 0.65 −1.03 777 0.32 −1.72 778 −1.64 −0.69 779 −0.68 1.75 780 0.34 1.73 781 −1.71 0.00 782 0.35 3.25 783 0.00 0.36 784 0.00 0.73 785 2.13 −1.12 786 1.43 0.74 787 1.06 0.00 788 0.70 0.00 789 2.76 0.73 790 1.41 3.24 791 1.05 −0.37 792 −0.36 0.00 793 −0.71 2.27 794 −1.46 3.03 795 0.73 1.12 796 −0.36 0.74 797 0.37 −1.11 798 −1.08 0.74 799 1.09 1.14 800 −0.37 1.88

The spectrum obtained from fluorescence spectroscopy is wavelength vs. absorption unit. The FSMI is then calculated by taking the sum of each absorbance unit at each wavelength (integer) and then dividing by 1000.

Applying equation (1), FSMI for the oil “AM” under investigation was calculated to be 15.639. The FSMI for all of the oils shown in FIG. 1 was similarly calculated, and is shown in Table 5, below.

TABLE 5 AM AH L1 SSL XSL UR BI IHI MB API 28.8 27.4 30.3 30.2 36.8 31.6 30.8 30.0 19.6 Gravity, ° FSMI 15.639 32.086 38.436 11.951 37.938 50.243 38.549 42.667 34.691

Applying equation (3) and the constants from Table 3, for the oil “AM” under review:

Cetane  Number_(GO)(CET) = K_(CET) + X 1_(CET) * DEN + X 2_(CET) * DEN² + X 3_(CET) * DEN³ + X 4_(CET) * FSMI + X 5_(CET) * FSMI² + X 6_(CET) * FSMI³ + X 7_(CET) * DEN * FSMI = (−2.920657 E + 04) + (8.247657 E + 04)(0.8828) + (−8.008823 E + 04)(0.8828)² + (2.758504 E + 04)(0.8828)³ + (1.273387 E + 02)(15.369) + (4.207752 E − 01)(15.369)² + (−4.676128 E − 03)(15.369)³ + (−1.581570 E + 02)(0.8828)(15.369) = 59 Pour  Point_(GO)(PP) = K_(PP) + X 1_(PP) * DEN + X 2_(PP) * DEN² + X 3_(PP) * DEN³ + X 4_(PP) * FSMI + X 5_(PP) * FSMI² + X 6_(PP) * FSMI³ + X 7_(PP) * DEN * FSMI = (−2.283807 E + 04) + (6.995129 E + 04)(0.8828) + (−7.232753 E + 04)(0.8828)² + (2.532512 E + 04)(0.8828)³ + (4.791017 E + 01)(15.369) + (−8.303909 E − 02)(15.369)² + (7.142002 E − 04)(15.369)³ + (−5.156225 E + 01)(0.8828)(15.369) = −10 Cloud  Point_(GO)(CP) = K_(CP) + X 1_(CP) * DEN + X 2_(CP) * DEN² + X 3_(CP) * DEN³ + X 4_(CP) * FSMI + X 5_(CP) * FSMI² + X 6_(CP) * FSMI³ + X 7_(CP) * DEN * FSMI = (8.016178 E + 04) + (−2.781445 E + 05)(0.8828) + (3.199487 E + 05)(0.8828)² + (−1.219746 E + 05)(0.8828)³ + (3.108188 E + 01)(15.369) + (1.963374 E − 01)(15.369)² + (−1.983566 E − 03)(15.369)³ + (−4.212763 E + 01)(0.8828)(15.369) = −10 Aniline  Point_(GO)(AP) = K_(AP) + X 1_(AP) * DEN + X 2_(AP) * DEN² + X 3_(AP) * DEN³ + X 4_(AP) * FSMI + X 5_(AP) * FSMI² + X 6_(AP) * FSMI³ + X 7_(AP) * DEN * FSMI = (−4.370054 E + 04) + (1.44982 E + 05)(0.8828) + (−1.608909 E + 05)(0.8828)² + (5.979962 E + 04)(0.8828)³ + (2.649713 E + 01)(15.369) + (−5.686953 E − 02)(15.369)² + (3.346494 E − 04)(15.369)³ + (−2.749938 E + 01)(0.8828)(15.369) = 66 Aromaticity_(WCO)(AROM) = K_(AROM) + X 1_(AROM) * DEN + X 2_(AROM) * DEN² + X 3_(AROM) * DEN³ + X 4_(AROM) * FSMI + X 5_(AROM) * FSMI² + X 6_(AROM) * FSMI³ + X 7_(AROM) * DEN * FSMI = (1.047903 E + 04) + (−4.741776 E + 04)(0.8828) + (6.274074 E + 04)(0.8828)² + (−2.516125 E + 04)(0.8828)³ + (8.586987 E + 01)(15.369) + (6.843602 E − 01)(15.369)² + (−7.078907 E − 03)(15.369)³ + (−1.207479 E + 02)(0.8828)(15.369) = 20 Octane  Number  (ON) = K_(ON) + X 1_(ON) * DEN + X 2_(ON) * DEN² + X 3_(ON) * DEN³ + X 4_(ON) * FSMI + X 5_(ON) * FSMI² + X 6_(ON) * FSMI³ + X 7_(ON) * DEN * FSMI = (8.202192 E + 05) + (−2.845858 E + 06)(0.8828) + (3.290683 E + 06)(0.8828)² + (−1.268002 E + 06)(0.8828)³ + (−1.182558 E + 01)(15.369) + (2.582860 E − 00)(15.369)² + (−1.277980 E − 01)(15.369)³ + (0)(0.8828)(15.369) = 52

Accordingly, as shown in the above example, indicative properties including cetane number, pour point, cloud point, aniline point, and aromaticity can be assigned to the crude oil samples without fractionation/distillation (crude oil assays).

In alternate embodiments, the present invention can be implemented as a computer program product for use with a computerized computing system. Those skilled in the art will readily appreciate that programs defining the functions of the present invention can be written in any appropriate programming language and delivered to a computer in any form, including but not limited to: (a) information permanently stored on non-writeable storage media (e.g., read-only memory devices such as ROMs or CD-ROM disks); (b) information alterably stored on writeable storage media (e.g., floppy disks and hard drives); and/or (c) information conveyed to a computer through communication media, such as a local area network, a telephone network, or a public network such as the Internet. When carrying computer readable instructions that implement the present invention methods, such computer readable media represent alternate embodiments of the present invention.

As generally illustrated herein, the system embodiments can incorporate a variety of computer readable media that comprise a computer usable medium having computer readable code means embodied therein. One skilled in the art will recognize that the software associated with the various processes described can be embodied in a wide variety of computer accessible media from which the software is loaded and activated. Pursuant to In re Beauregard, 35 U.S.P.Q.2d 1383 (U.S. Pat. No. 5,710,578), the present invention contemplates and includes this type of computer readable media within the scope of the invention. In certain embodiments, pursuant to In re Nuijten, 500 F.3d 1346 (Fed. Cir. 2007) (U.S. patent application Ser. No. 09/211,928), the scope of the present claims is limited to computer readable media, wherein the media is both tangible and non-transitory.

The system and method of the present invention have been described above and with reference to the attached figures; however, modifications will be apparent to those of ordinary skill in the art and the scope of protection for the invention is to be defined by the claims that follow. 

We claim:
 1. A system for evaluating a crude oil sample and calculating an indicative property of a naphtha or gas oil fraction of the crude oil sample without first distilling said naphtha or gas oil fraction, the system comprising: a fluorometer that outputs fluorescence spectroscopy data; a non-volatile memory device that stores calculation modules and data, the data including density of the crude oil sample and fluorescence spectroscopy data indicative of absorbance units at predetermined increments between a predetermined range for the oil sample, as derived by an analysis of the crude oil sample by the fluorometer; a processor coupled to the non-volatile memory; a first calculation module that retrieves the fluorescence spectroscopy data from the non-volatile memory device, calculates a crude oil fluorescence spectroscopy index value of the fraction from the absorbance units of the fluorescence spectroscopy data, and transfers the calculated crude oil fluorescence spectroscopy index value into the non-volatile memory; and a second calculation module that calculates the indicative property for the naphtha or gas oil fraction of the crude oil from a two-variable polynomial equation with predetermined constant coefficients developed using linear regression techniques, and that stores the indicative property into the non-volatile memory device; wherein the two variables of the two-variable polynomial equation are the crude oil fluorescence spectroscopy index and the density of the crude oil sample.
 2. The system of claim 1, wherein the indicative property is the cetane number.
 3. The system of claim 1, wherein the indicative property is the pour point.
 4. The system of claim 1, wherein the indicative property is the cloud point.
 5. The system of claim 1, wherein the indicative property is the aniline point.
 6. The system of claim 1, wherein the indicative property is the aromaticity.
 7. The system of claim 1, wherein the indicative property is the octane number.
 8. The system of claim 1, wherein the temperature range for the fluorometer is 20-1000° C.
 9. The system of claim 1, wherein the fluorescence spectroscopy index is that of whole crude oil.
 10. The system of claim 1, wherein the fluorescence spectroscopy index is calculated from fluorescence spectroscopy data measured in the wavelength range of 250-800 nm.
 11. The system of claim 1, wherein the fluorescence spectroscopy data is obtained directly from core and/or drill cuttings material.
 12. A method for evaluating a crude oil sample and calculating an indicative property of a naphtha or gas oil fraction of the crude oil sample without first distilling said naphtha or gas oil fraction, the method comprising: obtaining density of the crude oil sample; providing a fluorometer that outputs fluorescence spectroscopy data subjecting said crude oil sample to fluorescence spectroscopy analysis using the fluorometer, and entering absorbance units of the fluorescence spectroscopy data into non-volatile memory of a computer; using a processor of the computer to calculate a crude oil fluorescence spectroscopy index value of the fraction from the absorbance units of the spectroscopy data; and using the processor to calculate and enter into the non-volatile memory the indicative property for the naphtha or gas oil fraction of the crude oil from a two-variable polynomial equation with predetermined constant coefficients developed using linear regression techniques; wherein the two variables of the two-variable polynomial equation are the crude oil fluorescence spectroscopy index and the density of the crude oil sample.
 13. The method of claim 12, wherein the indicative property is the cetane number.
 14. The method of claim 12, wherein the indicative property is the pour point.
 15. The method of claim 12, wherein the indicative property is the cloud point.
 16. The method of claim 12, wherein the indicative property is the aniline point.
 17. The method of claim 12, wherein the indicative property is the aromaticity.
 18. The method of claim 12, wherein the indicative property is the octane number.
 19. The method of claim 12, wherein the temperature range for the fluorometer is 20-1000° C.
 20. The method of claim 12, wherein the fluorescence spectroscopy index is that of whole crude oil.
 21. The method of claim 12, wherein the fluorescence spectroscopy index is calculated from fluorescence spectroscopy data measured in the wavelength range of 250-800 nm.
 22. The method of claim 12, wherein the fluorescence spectroscopy data is obtained directly from core and/or drill cuttings material. 